Thanks so much, Edie, Jan, Katie, Mandy, Barb, Kathy, and PJ. I started with the blue, and used 3 deepening shades. Then I moved a bit on the color chart into the greens, at the same "depth" (intensity? saturation?), and made 3 shades getting lighter. And so on, ever closer to the red end, always switching between getting darker and getting lighter, and always trying to stay in that 3-step set of intensity. I didn't know how it would work out, but I liked the result, and I'm glad you all did, too! :-)))